Intravascular ultrasound imaging systems (IVUS) are used to obtain ultrasound images inside a patient's body. An IVUS system typically includes an ultrasound catheter having a flexible catheter sheath adapted for insertion into the vascular system of the patient. To obtain ultrasound images, the catheter comprises an imaging core received within a lumen of the catheter sheath. The imaging core comprises an ultrasound transducer attached to the distal end of a long flexible drive cable and an electrical and mechanical connector at the proximal end of the drive cable. The drive cable is used to rotate and longitudinally translate the transducer within the catheter lumen to obtain images at different positions within the patient's body.
The catheter may include a telescoping section that allows the imaging core to be advanced and pulled back within the catheter sheath to image a certain distance (e.g., 150 mm) along a blood vessel. The telescoping section may comprise an outer sheath and an inner sheath that slides within the outer sheath. The electrical and mechanical connector of the imaging core is mated to a mating connector of a motor drive unit (MDU), which rotates the drive cable of the imaging core and couples electrical signals between the imaging core and an ultrasound console.
During an imaging procedure, the imaging core may be automatically pulled back within the catheter sheath by a linear motor to image along a certain distance of a blood vessel. To do this, the outer sheath of the catheter's telescoping section is held fixed by a support. The inner sheath of the catheter's telescoping section is coupled to a motor drive that is automatically pulled away from the support causing the telescoping section to expand and the imaging core within the catheter sheath to move proximally within the blood vessel. As the imaging core is pulled back, the imaging core acquires images along the blood vessel. Typically, the imaging core is advanced within the catheter sheath manually by the physician. This is because the physician can feel an obstruction as the imaging core is manually advanced, and stop advancement when the physician encounters resistance caused by the obstruction.
A physician may choose to perform a manual pullback instead of an automatic pullback. Currently, the motor drive unit must be moved back, typically by the physician's assistant, to perform the manual pullback.
Current IVUS systems suffer from several drawbacks. One drawback is that the MDU is in the sterile field and therefore must be covered, e.g., by a sterile bag, which increases the setup time. Also, the physician must handle the MDU to guide the catheter into the patient and manually advance and pullback the imaging core, which complicates the procedure and increases the risk of the MDU being accidentally dropped. Further, the MDU may get in the way of the physician during the procedure.